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@webda/coreReadme | API


Class: FileQueue<T, K>

FIFO Queue on filesystem

Webda Modda

Extends

Type parameters

T = any

K extends FileQueueParameters = FileQueueParameters

Constructors

new FileQueue(webda, name, params)

new FileQueue<T, K>(webda, name, params): FileQueue<T, K>

Parameters

webda: Core<CoreEvents>

The main instance of Webda

name: string

The name of the service

params: DeepPartial<K>= {}

The parameters block define in the configuration file

Returns

FileQueue<T, K>

Inherited from

Queue.constructor

Source

packages/core/src/services/service.ts:334

Properties

_createException

_createException: string

Inherited from

Queue._createException

Source

packages/core/src/services/service.ts:315


_initException

_initException: any = undefined

Inherited from

Queue._initException

Source

packages/core/src/services/service.ts:317


_initTime

_initTime: number

Inherited from

Queue._initTime

Source

packages/core/src/services/service.ts:316


_name

protected _name: string

Service name

Inherited from

Queue._name

Source

packages/core/src/services/service.ts:308


_timeout

protected _timeout: Timeout

Current timeout handler

Inherited from

Queue._timeout

Source

packages/core/src/queues/queueservice.ts:69


_webda

protected _webda: Core<CoreEvents>

Webda Core object

Inherited from

Queue._webda

Source

packages/core/src/services/service.ts:304


delayer

protected delayer: WaitDelayer

Delayer

Inherited from

Queue.delayer

Source

packages/core/src/queues/queueservice.ts:81


eventPrototype

eventPrototype: () => T

Returns

T

Inherited from

Queue.eventPrototype

Source

packages/core/src/queues/queueservice.ts:82


failedIterations

protected failedIterations: number

Current pause instance

Inherited from

Queue.failedIterations

Source

packages/core/src/queues/queueservice.ts:77


logger

protected logger: Logger

Logger with class context

Inherited from

Queue.logger

Source

packages/core/src/services/service.ts:321


metrics

protected metrics: Object

Type declaration

errors

errors: Counter<string>

messages_pending

messages_pending: Gauge<string>

messages_received

messages_received: Counter<string>

messages_sent

messages_sent: Counter<string>

processing_duration

processing_duration: Histogram<string>

Inherited from

Queue.metrics

Source

packages/core/src/queues/pubsubservice.ts:12


parameters

protected parameters: K

Hold the parameters for your service

It will be bring from the webda.config.json

Inherited from

Queue.parameters

Source

packages/core/src/services/service.ts:314


captureRejectionSymbol

static readonly captureRejectionSymbol: typeof captureRejectionSymbol

Inherited from

Queue.captureRejectionSymbol

Source

packages/core/node_modules/@types/node/events.d.ts:328


captureRejections

static captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

Inherited from

Queue.captureRejections

Source

packages/core/node_modules/@types/node/events.d.ts:333


defaultMaxListeners

static defaultMaxListeners: number

Inherited from

Queue.defaultMaxListeners

Source

packages/core/node_modules/@types/node/events.d.ts:334


errorMonitor

static readonly errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an 'error' event is emitted, therefore the process will still crash if no regular 'error' listener is installed.

Inherited from

Queue.errorMonitor

Source

packages/core/node_modules/@types/node/events.d.ts:327

Methods

__clean()

__clean(): Promise<void>

Clean the service data, can only be used in test mode

Returns

Promise<void>

Overrides

Queue.__clean

Abstract

Source

packages/core/src/queues/filequeue.ts:145


addListener()

addListener(eventName, listener): this

Alias for emitter.on(eventName, listener).

Parameters

eventName: string | symbol

listener: (...args) => void

Returns

this

Inherited from

Queue.addListener

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:354


addRoute()

protected addRoute(url, methods, executer, openapi, override): void

Add a route dynamicaly

Parameters

url: string

of the route can contains dynamic part like {uuid}

methods: HttpMethodType[]

executer: Function

Method to execute for this route

openapi: OpenAPIWebdaDefinition= {}

override: boolean= false

Returns

void

Inherited from

Queue.addRoute

Source

packages/core/src/services/service.ts:482


authorizeClientEvent()

authorizeClientEvent(_event, _context): boolean

Authorize a public event subscription

Parameters

_event: string

_context: OperationContext<any, any>

Returns

boolean

Inherited from

Queue.authorizeClientEvent

Source

packages/core/src/services/service.ts:438


computeParameters()

computeParameters(): void

Create the storage folder if does not exist

Returns

void

Overrides

Queue.computeParameters

Source

packages/core/src/queues/filequeue.ts:43


consume()

consume(callback, eventPrototype?): CancelablePromise<void>

Work a queue calling the callback with every Event received If the callback is called without exception the deleteMessage is called

Parameters

callback: (event) => Promise<void>

eventPrototype?: () => T

Returns

CancelablePromise<void>

Inherited from

Queue.consume

Source

packages/core/src/queues/queueservice.ts:172


consumerReceiveMessage()

protected consumerReceiveMessage(): Promise<Object>

Receive and process message from the queue

Returns

Promise<Object>

items

items: number

speed

speed: number

Inherited from

Queue.consumerReceiveMessage

Source

packages/core/src/queues/queueservice.ts:109


deleteMessage()

deleteMessage(receipt): Promise<void>

Delete one message based on its receipt

Parameters

receipt: any

Returns

Promise<void>

Overrides

Queue.deleteMessage

Source

packages/core/src/queues/filequeue.ts:132


emit()

emit<Key>(event, data): boolean

Override to allow capturing long listeners

Type parameters

Key extends string | number

Parameters

event: symbol | Key

data: Events[Key]

Returns

boolean

Inherited from

Queue.emit

Source

packages/core/src/services/service.ts:596


emitSync()

emitSync<Key>(event, data): Promise<any[]>

Emit the event with data and wait for Promise to finish if listener returned a Promise

Type parameters

Key extends string | number

Parameters

event: Key

data: Events[Key]

Returns

Promise<any[]>

Inherited from

Queue.emitSync

Source

packages/core/src/services/service.ts:588


eventNames()

eventNames(): (string | symbol)[]

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

const EventEmitter = require('events');
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns

(string | symbol)[]

Inherited from

Queue.eventNames

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:669


getClientEvents()

getClientEvents(): string[]

Return the events that an external system can subscribe to

Returns

string[]

Inherited from

Queue.getClientEvents

Source

packages/core/src/services/service.ts:429


getFile()

getFile(uid): string

Return file

Parameters

uid: string

Returns

string

Source

packages/core/src/queues/filequeue.ts:62


getMaxConsumers()

getMaxConsumers(): number

Return the max consumers for the queue

It is overridable so if a queue can retrieve several message at once it can just use the worker // and several messages at once

SQS for example will return this.parameters.maxConsumers / 10

Returns

number

Inherited from

Queue.getMaxConsumers

Source

packages/core/src/queues/queueservice.ts:162


getMaxListeners()

getMaxListeners(): number

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.

Returns

number

Inherited from

Queue.getMaxListeners

Since

v1.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:526


getMetric()

getMetric<T>(type, configuration): T

Add service name label

Type parameters

T = Counter<string> | Histogram<string> | Gauge<string>

Parameters

type: Constructor<T, [MetricConfiguration<T>]>

configuration: MetricConfiguration<T>

Returns

T

Inherited from

Queue.getMetric

Source

packages/core/src/services/service.ts:414


getName()

getName(): string

Get service name

Returns

string

Inherited from

Queue.getName

Source

packages/core/src/services/service.ts:633


getOpenApiReplacements()

getOpenApiReplacements(): any

Return variables for replacement in openapi

Returns

any

Inherited from

Queue.getOpenApiReplacements

Source

packages/core/src/services/service.ts:507


getOperationId()

getOperationId(id): string

If undefined is returned it cancel the operation registration

Parameters

id: string

Returns

string

Inherited from

Queue.getOperationId

Source

packages/core/src/services/service.ts:471


getParameters()

getParameters(): K

Get the service parameters

Returns

K

Inherited from

Queue.getParameters

Source

packages/core/src/services/service.ts:359


getService()

getService<K>(service): K

Return a webda service

Type parameters

K extends Service<ServiceParameters, Events>

Parameters

service: string

name to retrieve

Returns

K

Inherited from

Queue.getService

Source

packages/core/src/services/service.ts:626


getUrl()

getUrl(url, _methods): string

Return the full path url based on parameters

Parameters

url: string

relative url to service

_methods: HttpMethodType[]

in case we need filtering (like Store)

Returns

string

absolute url or undefined if need to skip the Route

Inherited from

Queue.getUrl

Source

packages/core/src/services/service.ts:449


getWebda()

getWebda(): Core<CoreEvents>

Return WebdaCore

Returns

Core<CoreEvents>

Inherited from

Queue.getWebda

Source

packages/core/src/services/service.ts:366


init()

init(): Promise<FileQueue<T, K>>

Will be called after all the Services are created

Returns

Promise<FileQueue<T, K>>

Inherited from

Queue.init

Abstract

Source

packages/core/src/services/service.ts:570


initMetrics()

initMetrics(): void

Returns

void

Inherited from

Queue.initMetrics

Source

packages/core/src/queues/pubsubservice.ts:22


initOperations()

initOperations(): void

Init the operations

Returns

void

Inherited from

Queue.initOperations

Source

packages/core/src/services/service.ts:528


initRoutes()

initRoutes(): void

Init the routes

Returns

void

Inherited from

Queue.initRoutes

Source

packages/core/src/services/service.ts:514


listenerCount()

listenerCount(eventName): number

Returns the number of listeners listening to the event named eventName.

Parameters

eventName: string | symbol

The name of the event being listened for

Returns

number

Inherited from

Queue.listenerCount

Since

v3.2.0

Source

packages/core/node_modules/@types/node/events.d.ts:616


listeners()

listeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Parameters

eventName: string | symbol

Returns

Function[]

Inherited from

Queue.listeners

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:539


loadParameters()

loadParameters(params): ServiceParameters

Load the parameters for a service

Parameters

params: any

Returns

ServiceParameters

Overrides

Queue.loadParameters

Source

packages/core/src/queues/filequeue.ts:36


log()

log(level, ...args): void

Parameters

level: WorkerLogLevel

to log

• ...args: any[]

Returns

void

Inherited from

Queue.log

Source

packages/core/src/services/service.ts:662


off()

off(eventName, listener): this

Alias for emitter.removeListener().

Parameters

eventName: string | symbol

listener: (...args) => void

Returns

this

Inherited from

Queue.off

Since

v10.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:499


on()

on<Key>(event, listener): this

Type the listener part

Type parameters

Key extends string | number

Parameters

event: symbol | Key

listener: (evt) => void

Returns

this

Inherited from

Queue.on

Source

packages/core/src/services/service.ts:607


onAsync()

onAsync<Key>(event, listener, queue): void

Listen to an event as on(...) would do except that it will be asynchronous

Type parameters

Key extends string | number

Parameters

event: Key

listener: (evt) => void

queue: string= undefined

Name of queue to use, can be undefined, queue name are used to define differents priorities

Returns

void

Inherited from

Queue.onAsync

Source

packages/core/src/services/service.ts:618


once()

once(eventName, listener): this

Adds a one-timelistener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a

Parameters

eventName: string | symbol

The name of the event.

listener: (...args) => void

The callback function

Returns

this

Inherited from

Queue.once

Since

v0.3.0

Source

packages/core/node_modules/@types/node/events.d.ts:414


prependListener()

prependListener(eventName, listener): this

Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => {
console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

eventName: string | symbol

The name of the event.

listener: (...args) => void

The callback function

Returns

this

Inherited from

Queue.prependListener

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:634


prependOnceListener()

prependOnceListener(eventName, listener): this

Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

eventName: string | symbol

The name of the event.

listener: (...args) => void

The callback function

Returns

this

Inherited from

Queue.prependOnceListener

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:650


rawListeners()

rawListeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Parameters

eventName: string | symbol

Returns

Function[]

Inherited from

Queue.rawListeners

Since

v9.4.0

Source

packages/core/node_modules/@types/node/events.d.ts:569


receiveMessage()

receiveMessage<L>(proto?): Promise<MessageReceipt<L>[]>

Receive one or several messages

Type parameters

L

Parameters

proto?: () => L

Returns

Promise<MessageReceipt<L>[]>

Overrides

Queue.receiveMessage

Source

packages/core/src/queues/filequeue.ts:83


reinit()

reinit(config): Promise<FileQueue<T, K>>

Parameters

config: DeepPartial<K>

new parameters for the service

Returns

Promise<FileQueue<T, K>>

Inherited from

Queue.reinit

Source

packages/core/src/services/service.ts:579


removeAllListeners()

removeAllListeners(event?): this

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

event?: string | symbol

Returns

this

Inherited from

Queue.removeAllListeners

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:510


removeListener()

removeListener(eventName, listener): this

Removes the specified listener from the listener array for the event namedeventName.

const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.

const myEmitter = new MyEmitter();

const callbackA = () => {
console.log('A');
myEmitter.removeListener('event', callbackB);
};

const callbackB = () => {
console.log('B');
};

myEmitter.on('event', callbackA);

myEmitter.on('event', callbackB);

// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
// A
// B

// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
// A

Because listeners are managed using an internal array, calling this will change the position indices of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping')listener is removed:

const ee = new EventEmitter();

function pong() {
console.log('pong');
}

ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);

ee.emit('ping');
ee.emit('ping');

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

eventName: string | symbol

listener: (...args) => void

Returns

this

Inherited from

Queue.removeListener

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:494


resolve()

resolve(): this

Create the delayer

Returns

this

Inherited from

Queue.resolve

Source

packages/core/src/queues/queueservice.ts:98


sendMessage()

sendMessage(params): Promise<void>

Send an event to the queue

Parameters

params: any

Returns

Promise<void>

Overrides

Queue.sendMessage

Source

packages/core/src/queues/filequeue.ts:69


setMaxListeners()

setMaxListeners(n): this

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

n: number

Returns

this

Inherited from

Queue.setMaxListeners

Since

v0.3.5

Source

packages/core/node_modules/@types/node/events.d.ts:520


size()

size(): Promise<number>

Size of the consumer if any

Returns

Promise<number>

Overrides

Queue.size

Source

packages/core/src/queues/filequeue.ts:53


stop()

stop(): Promise<void>

Shutdown the current service if action need to be taken

Returns

Promise<void>

Inherited from

Queue.stop

Source

packages/core/src/services/service.ts:373


toJSON()

toJSON(): string

Prevent service to be serialized

Returns

string

Inherited from

Queue.toJSON

Source

packages/core/src/services/service.ts:560


toPublicJSON()

toPublicJSON(object): string

Convert an object to JSON using the Webda json filter

Parameters

object: unknown

The object to export

Returns

string

The export of the strip object ( removed all attribute with _ )

Inherited from

Queue.toPublicJSON

Source

packages/core/src/services/service.ts:552


toString()

toString(): string

Return service representation

Returns

string

Inherited from

Queue.toString

Source

packages/core/src/services/service.ts:380


unserialize()

unserialize<L>(data, proto?): L

Unserialize into class

Type parameters

L

Parameters

data: string

proto?: () => L

Returns

L

Inherited from

Queue.unserialize

Source

packages/core/src/queues/pubsubservice.ts:57


getEventListeners()

static getEventListeners(emitter, name): Function[]

Returns a copy of the array of listeners for the event named eventName.

For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

const { getEventListeners, EventEmitter } = require('events');

{
const ee = new EventEmitter();
const listener = () => console.log('Events are fun');
ee.on('foo', listener);
getEventListeners(ee, 'foo'); // [listener]
}
{
const et = new EventTarget();
const listener = () => console.log('Events are fun');
et.addEventListener('foo', listener);
getEventListeners(et, 'foo'); // [listener]
}

Parameters

emitter: EventEmitter | _DOMEventTarget

name: string | symbol

Returns

Function[]

Inherited from

Queue.getEventListeners

Since

v15.2.0, v14.17.0

Source

packages/core/node_modules/@types/node/events.d.ts:299


listenerCount()

static listenerCount(emitter, eventName): number

A class method that returns the number of listeners for the given eventNameregistered on the given emitter.

const { EventEmitter, listenerCount } = require('events');
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2

Parameters

emitter: EventEmitter

The emitter to query

eventName: string | symbol

The event name

Returns

number

Inherited from

Queue.listenerCount

Since

v0.9.12

Deprecated

Since v3.2.0 - Use listenerCount instead.

Source

packages/core/node_modules/@types/node/events.d.ts:271


on()

static on(emitter, eventName, options?): AsyncIterableIterator<any>

const { on, EventEmitter } = require('events');

(async () => {
const ee = new EventEmitter();

// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});

for await (const event of on(ee, 'foo')) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();

Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

An AbortSignal can be used to cancel waiting on events:

const { on, EventEmitter } = require('events');
const ac = new AbortController();

(async () => {
const ee = new EventEmitter();

// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});

for await (const event of on(ee, 'foo', { signal: ac.signal })) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();

process.nextTick(() => ac.abort());

Parameters

emitter: EventEmitter

eventName: string

The name of the event being listened for

options?: StaticEventEmitterOptions

Returns

AsyncIterableIterator<any>

that iterates eventName events emitted by the emitter

Inherited from

Queue.on

Since

v13.6.0, v12.16.0

Source

packages/core/node_modules/@types/node/events.d.ts:254


once()

once(emitter, eventName, options)

static once(emitter, eventName, options?): Promise<any[]>

Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

const { once, EventEmitter } = require('events');

async function run() {
const ee = new EventEmitter();

process.nextTick(() => {
ee.emit('myevent', 42);
});

const [value] = await once(ee, 'myevent');
console.log(value);

const err = new Error('kaboom');
process.nextTick(() => {
ee.emit('error', err);
});

try {
await once(ee, 'myevent');
} catch (err) {
console.log('error happened', err);
}
}

run();

The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

const { EventEmitter, once } = require('events');

const ee = new EventEmitter();

once(ee, 'error')
.then(([err]) => console.log('ok', err.message))
.catch((err) => console.log('error', err.message));

ee.emit('error', new Error('boom'));

// Prints: ok boom

An AbortSignal can be used to cancel waiting for the event:

const { EventEmitter, once } = require('events');

const ee = new EventEmitter();
const ac = new AbortController();

async function foo(emitter, event, signal) {
try {
await once(emitter, event, { signal });
console.log('event emitted!');
} catch (error) {
if (error.name === 'AbortError') {
console.error('Waiting for the event was canceled!');
} else {
console.error('There was an error', error.message);
}
}
}

foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!
Parameters

emitter: _NodeEventTarget

eventName: string | symbol

options?: StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

Queue.once

Since

v11.13.0, v10.16.0

Source

packages/core/node_modules/@types/node/events.d.ts:194

once(emitter, eventName, options)

static once(emitter, eventName, options?): Promise<any[]>

Parameters

emitter: _DOMEventTarget

eventName: string

options?: StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

Queue.once

Source

packages/core/node_modules/@types/node/events.d.ts:195


setMaxListeners()

static setMaxListeners(n?, ...eventTargets?): void

const {
setMaxListeners,
EventEmitter
} = require('events');

const target = new EventTarget();
const emitter = new EventEmitter();

setMaxListeners(5, target, emitter);

Parameters

n?: number

A non-negative number. The maximum number of listeners per EventTarget event.

• ...eventTargets?: (EventEmitter | _DOMEventTarget)[]

Returns

void

Inherited from

Queue.setMaxListeners

Since

v15.4.0

Source

packages/core/node_modules/@types/node/events.d.ts:317